Marlon Wayans -- Bruce Jenner Should Just 'Get the Breasts Already'

We broke the story, Bruce already consulted a plastic surgeon about reducing the size of his adam's apple -- though Bruce insists it's NOT the first step of gender reassignment, it's just because he doesn't like the way his throat looks.

Still, Marlon ain't buyin' Bruce's explanation -- and on his way out a "What the Funny" event he told us, "I think slowly but surely he's been turning himself into a woman all these years."

"Why don't Bruce Jenner just go and get the titties now ... just get the breasts."

In the end, Marlon says if Bruce continues down the surgery path ... "He's gonna look like me in 'White Chicks.'"